Battery operated radio tags are often used to tag objects for use over a distance longer than that radio powered tags can provide. Battery operated tags are also often used to reduce power consumption of their reader device as then the reader device need not transmit such a high radio power that the electronics within surrounding passive tags could be so powered.
New Bluetooth® version 4 specifies a standardized version of Smart Devices that consume relatively little power by practically switching off until some event triggers them on. Some examples are a heart rate monitor that sends data only when a given heart rate is exceeded and a wireless thermometer that can be paired and maintained operable for a number of days but sends a reading immediately when used to take a child's temperature.
Bluetooth v4.0 specification has a low energy Find Me profile for smartphone applications that allows users to pair small, often misplaced, objects with their smartphones for locating them when needed. For instance, a Bluetooth low energy proximity key fob is usable to find a misplaced phone using a button on the fob to make the paired smartphone to issue an audible signal. Correspondingly, a misplaced key fob can be found by using the paired smartphone to make the key fob sound an alert. To this end, the key fob should periodically listen to polling signals to detect radio signals sent from the smartphone. However, periodical awakening of the Bluetooth functionality necessarily consumes power and the key fob with Find Me profile operability is useless if it has run out of battery.